Vernalization promotes bolting in sugar beet by inhibiting the transcriptional repressors of BvGI.

Sugar beet (Beta vulgaris L.), a biennial sugar crop, contributes about 16% of the world's sugar production. The transition from vegetative growth, during which sugar accumulated in beet, to reproductive growth, during which sugar exhausted in beet, is determined by vernalization and photoperiod. GIGANTEA (GI) is a key photoperiodic flowering gene that is induced by vernalization in sugar beet. To identify the upstream regulatory factors of BvGI, candidate transcription factors (TF) that were co-expressed with BvGI and could bind to the BvGI promoter were screened based on weighted gene co-expression network analysis (WGCNA) and TF binding site prediction. Subsequently, their transcriptional regulatory role on the BvGI was validated through subcellular localization, dual-luciferase assays and yeast transformation tests. A total of 7,586 differentially expressed genes were identified after vernalization and divided into 18 co-expression modules by WGCNA, of which one (MEcyan) and two (MEdarkorange2 and MEmidnightblue) modules were positively and negatively correlated with the expression of BvGI, respectively. TF binding site predictions using PlantTFDB enabled the screening of BvLHY, BvTCP4 and BvCRF4 as candidate TFs that negatively regulated the expression of BvGI by affecting its transcription. Subcellular localization showed that BvLHY, BvTCP4 and BvCRF4 were localized to the nucleus. The results of dual-luciferase assays and yeast transformation tests showed that the relative luciferase activity and expression of HIS3 was reduced in the BvLHY, BvTCP4 and BvCRF4 transformants, which suggested that the three TFs inhibited the BvGI promoter. In addition, real-time quantitative reverse transcription PCR showed that BvLHY and BvTCP4 exhibited rhythmic expression characteristics similar to that of BvGI, while BvCRF4 did not. Our results revealed that vernalization crosstalked with the photoperiod pathway to initiate bolting in sugar beet by inhibiting the transcriptional repressors of BvGI.

Effect of BvAgNP on growth, development, and glyoxalase gene expression analysis in Mammillaria bombycina and Selenicereus undatus.

BACKGROUND: Silver nanoparticles (AgNPs) have been used in plant tissue culture as growth stimulants, promoting bud initiation, germination, and rooting. In prior studies, AgNPs were synthesized and characterized by green synthesis using extracts from Beta vulgaris var. cicla (BvAgNP), and their functionality as seed disinfectant and antimicrobial was verified. In this study, we evaluated the effect of BvAgNP on the growth and development of Mammillaria bombycina and Selenicereus undatus in vitro, as well as the expression of glyoxalase genes. METHODS: Explants from M. bombycina and S. undatus in vitro were treated with 25, 50, and 100 mg/L of BvAgNP. After 90 days, morphological characteristics were evaluated, and the expression of glyoxalase genes was analyzed by qPCR. RESULTS: All treatments inhibited rooting for M. bombycina and no bud initiation was observed. S. undatus, showed a maximum response in rooting and bud generation at 25 mg/L of BvAgNP. Scanning electron microscopy (SEM) results exhibited a higher number of vacuoles in stem cells treated with BvAgNP compared to the control for both species. Expression of glyoxalase genes in M. bombycina increased in all treatments, whereas it decreased for S. undatus, however, increasing in roots. CONCLUSIONS: This study presents the effects of BvAgNP on the growth and development of M. bombycina and S. undatus, with the aim of proposing treatments that promote in vitro rooting and bud initiation.

MicroRNAs Participate in Morphological Acclimation of Sugar Beet Roots to Nitrogen Deficiency.

Nitrogen (N) is essential for sugar beet (Beta vulgaris L.), a highly N-demanding sugar crop. This study investigated the morphological, subcellular, and microRNA-regulated responses of sugar beet roots to low N (LN) stress (0.5 mmol/L N) to better understand the N perception, uptake, and utilization in this species. The results showed that LN led to decreased dry weight of roots, N accumulation, and N dry matter production efficiency, along with damage to cell walls and membranes and a reduction in organelle numbers (particularly mitochondria). Meanwhile, there was an increase in root length (7.2%) and branch numbers (29.2%) and a decrease in root surface area (6.14%) and root volume (6.23%) in sugar beet after 7 d of LN exposure compared to the control (5 mmol/L N). Transcriptomics analysis was confirmed by qRT-PCR for 6 randomly selected microRNAs, and we identified 22 differentially expressed microRNAs (DEMs) in beet root under LN treatment. They were primarily enriched in functions related to binding (1125), ion binding (641), intracellular (437) and intracellular parts (428), and organelles (350) and associated with starch and sucrose metabolism, tyrosine metabolism, pyrimidine metabolism, amino sugar and nucleotide sugar metabolism, and isoquinoline alkaloid biosynthesis, as indicated by the GO and KEGG analyses. Among them, the upregulated miR156a, with conserved sequences, was identified as a key DEM that potentially targets and regulates squamosa promoter-binding-like proteins (SPLs, 104889216 and 104897537) through the microRNA-mRNA network. Overexpression of miR156a (MIR) promoted root growth in transgenic Arabidopsis, increasing the length, surface area, and volume. In contrast, silencing miR156a (STTM) had the opposite effect. Notably, the fresh root weight decreased by 45.6% in STTM lines, while it increased by 27.4% in MIR lines, compared to the wild type (WT). It can be inferred that microRNAs, especially miR156, play crucial roles in sugar beet root's development and acclimation to LN conditions. They likely facilitate active responses to N deficiency through network regulation, enabling beet roots to take up nutrients from the environment and sustain their vital life processes.

Zinc and methyl jasmonate improve sugar beet tolerance to high boron stress by enhanced leaf photochemical performance.

Nutrient imbalances, such as high boron (B) stress, occur within, as well as across, agricultural systems worldwide and have become an important abiotic factor that reduces soil fertility and inhibits plant growth. Sugar beet is a B-loving crop and is better suited to be grown in high B environments, but the methods and mechanisms regarding the enhancement of high-B stress tolerance traits are not clear. The main objective of this research was to elucidate the effects of the alone and/or combined foliar spraying of zinc sulfate (ZnSO4) and methyl jasmonate (MeJA) on the growth parameters, tolerance, and photochemical performance of sugar beet under high-B stress. Results demonstrated that the photosynthetic performance was inhibited under high-B stress, with a reduction of 11.33% in the net photosynthetic rate (Pn) and an increase of 25.30% in the tolerance index. The application of ZnSO4, MeJA, and their combination enhanced sugar beet's adaptability to high-B stress, with an increase in Pn of 9.22%, 4.49%, and 2.85%, respectively, whereas the tolerance index was elevated by 15.33%, 8.21%, and 5.19%, respectively. All three ameliorative treatments resulted in increased photochemical efficiency (Fv/Fm) and the photosynthetic performance index (PIABS) of PSII. Additionally, they enhanced the light energy absorption (ABS/RC) and trapping capacity (DIO/RC), reduced the thermal energy dissipation (TRO/RC), and facilitated the QA to QB transfer in the electron transport chain (ETC) of PSII, which collectively improved the photochemical performance. Therefore, spraying both ZnSO4 and MeJA can better alleviate high-B stress and promote the growth of sugar beet, but the combined spraying effect of ZnSO4 and MeJA is lower than that of individual spraying. This study provides a reference basis for enhancing the ability of sugar beet and other plants to tolerate high-B stress and for sugar beet cultivation in high B areas.

Optimizing biochar application for enhanced cotton and sugar beet production in Xinjiang: a comprehensive study.

BACKGROUND: Optimizing biochar application is vital for enhancing crop production and ensuring sustainable agricultural production. A 3-year field experiment was established to explore the effects of varying the biochar application rate (BAR) on crop growth, quality, productivity and yields. BAR was set at 0, 10, 50 and 100 t ha-1 in 2018; 0, 10, 25, 50 and 100 t ha-1 in 2019; and 0, 10, 25 and 30 t ha-1 in 2020. Crop quality and growth status and production were evaluated using the dynamic technique for order preference by similarity to ideal solution with the entropy weighted method (DTOPSIS-EW), principal component analysis (PCA), membership function analysis (MFA), gray relation analysis (GRA) and the fuzzy Borda combination evaluation method. RESULTS: Low-dose BAR (≤ 25 t ha-1 for cotton; ≤ 50 t ha-1 for sugar beet) effectively increased biomass, plant height, leaf area index (LAI), water and fertility (N, P and K) productivities, and yield. Biochar application increased the salt absorption and sugar content in sugar beet, with the most notable increases being 116.45% and 20.35%, respectively. Conversely, BAR had no significant effect on cotton fiber quality. The GRA method was the most appropriate for assessing crop growth and quality. The most indicative parameters for reflecting cotton and sugarbeet growth and quality status were biomass and LAI. The 10 t ha-1 BAR consistently produced the highest scores and was the most economically viable option, as evaluated by DTOPSIS-EW. CONCLUSION: The optimal biochar application strategy for improving cotton and sugar beet cultivation in Xinjiang, China, is 10 t ha-1 biochar applied continuously. © 2024 Society of Chemical Industry.

Cell-Wall-Degrading Enzymes-Related Genes Originating from Rhizoctonia solani Increase Sugar Beet Root Damage in the Presence of Leuconostoc mesenteroides.

Sugar beet crown and root rot caused by Rhizoctonia solani is a major yield constraint. Root rot is highly increased when R. solani and Leuconostoc mesenteroides co-infect roots. We hypothesized that the absence of plant cell-wall-degrading enzymes in L. mesenteroides and their supply by R. solani during close contact, causes increased damage. In planta root inoculation with or without cell-wall-degrading enzymes showed greater rot when L. mesenteroides was combined with cellulase (22 mm rot), polygalacturonase (47 mm), and pectin lyase (57 mm) versus these enzymes (0-26 mm), R. solani (20 mm), and L. mesenteroides (13 mm) individually. Carbohydrate analysis revealed increased simpler carbohydrates (namely glucose + galactose, and fructose) in the infected roots versus mock control, possibly due to the degradation of complex cell wall carbohydrates. Expression of R. solani cellulase, polygalacturonase, and pectin lyase genes during root infection corroborated well with the enzyme data. Global mRNAseq analysis identified candidate genes and highly co-expressed gene modules in all three organisms that might be critical in host plant defense and pathogenesis. Targeting R. solani cell-wall-degrading enzymes in the future could be an effective strategy to mitigate root damage during its interaction with L. mesenteroides.

Chloroplast nucleoids are highly dynamic in ploidy, number, and structure during angiosperm leaf development.

Chloroplast nucleoids are large, compact nucleoprotein structures containing multiple copies of the plastid genome. Studies on structural and quantitative changes of plastid DNA (ptDNA) during leaf development are scarce and have produced controversial data. We have systematically investigated nucleoid dynamics and ptDNA quantities in the mesophyll of Arabidopsis, tobacco, sugar beet, and maize from the early post-meristematic stage until necrosis. DNA of individual nucleoids was quantified by DAPI-based supersensitive epifluorescence microscopy. Nucleoids occurred in scattered, stacked, or ring-shaped arrangements and in recurring patterns during leaf development that was remarkably similar between the species studied. Nucleoids per organelle varied from a few in meristematic plastids to >30 in mature chloroplasts (corresponding to about 20-750 nucleoids per cell). Nucleoid ploidies ranged from haploid to >20-fold even within individual organelles, with average values between 2.6-fold and 6.7-fold and little changes during leaf development. DNA quantities per organelle increased gradually from about a dozen plastome copies in tiny plastids of apex cells to 70-130 copies in chloroplasts of about 7 µm diameter in mature mesophyll tissue, and from about 80 plastome copies in meristematic cells to 2600-3300 copies in mature diploid mesophyll cells without conspicuous decline during leaf development. Pulsed-field electrophoresis, restriction of high-molecular-weight DNA from chloroplasts and gerontoplasts, and CsCl equilibrium centrifugation of single-stranded and double-stranded ptDNA revealed no noticeable fragmentation of the organelle DNA during leaf development, implying that plastid genomes in mesophyll tissues are remarkably stable until senescence.

Plant mitochondria and chloroplasts are targeted by the Rhizoctonia solani RsCRP1 effector.

The fungal species Rhizoctonia solani belongs to the Basidiomycota division and is a ubiquitous soil-borne pathogen. It is the main agent of the damping-off disease in seedlings and causes the root and crown rot disease in sugar beets. Plant pathogens deploy small secreted proteins, called effectors, to manipulate plant immunity in order to infect the host. Here, a gene (RsCRP1) encoded a putative effector cysteine-rich protein was cloned, expressed in Cercospora beticola and used for virulence assays. The RsCRP1 gene was highly induced upon the early-infection stage of sugar beet seedlings and disease was promoted. Confocal microscopy demonstrated localization to the chloroplasts and mitochondria upon transient expression of RsCRP1 in leaves of Nicotiana benthamiana. Further, this effector was unable to induce necrosis or to suppress hypersensitive response induced by the Avr4/Cf4 complex in N. benthamiana. Overall, these data indicate that RsCRP1 is a novel effector targeting distinct plant cell organelles in order to facilitate a successful infection at the early stages of the disease development.

Identification of plant leaf phosphorus content at different growth stages based on hyperspectral reflectance.

BACKGROUND: Modern agriculture strives to sustainably manage fertilizer for both economic and environmental reasons. The monitoring of any nutritional (phosphorus, nitrogen, potassium) deficiency in growing plants is a challenge for precision farming technology. A study was carried out on three species of popular crops, celery (Apium graveolens L., cv. Neon), sugar beet (Beta vulgaris L., cv. Tapir) and strawberry (Fragaria × ananassa Duchesne, cv. Honeoye), fertilized with four different doses of phosphorus (P) to deliver data for non-invasive detection of P content. RESULTS: Data obtained via biochemical analysis of the chlorophyll and carotenoid contents in plant material showed that the strongest effect of P availability for plants was in the diverse total chlorophyll content in sugar beet and celery compared to that in strawberry, in which P affects a variety of carotenoid contents in leaves. The measurements performed using hyperspectral imaging, obtained in several different stages of plant development, were applied in a supervised classification experiment. A machine learning algorithm (Backpropagation Neural Network, Random Forest, Naive Bayes and Support Vector Machine) was developed to classify plants from four variants of P fertilization. The lowest prediction accuracy was obtained for the earliest measured stage of plant development. Statistical analyses showed correlations between leaf biochemical constituents, phosphorus fertilization and the mass of the leaf/roots of the plants. CONCLUSIONS: Obtained results demonstrate that hyperspectral imaging combined with artificial intelligence methods has potential for non-invasive detection of non-homogenous phosphorus fertilization on crop levels.

Plastic response to early shade avoidance cues has season-long effect on Beta vulgaris growth and development.

Early-emerging weeds are known to negatively affect crop growth but the mechanisms by which weeds reduce crop yield are not fully understood. In a 4-year study, we evaluated the effect of duration of weed-reflected light on sugar beet (Beta vulgaris L.) growth and development. The study included an early-season weed removal series and a late-season weed addition series of treatments arranged in a randomized complete block, and the study design minimized direct resource competition. If weeds were present from emergence until the two true-leaf sugar beet stage, sugar beet leaf area was reduced 22%, leaf biomass reduced 25%, and root biomass reduced 32% compared to sugar beet grown season-long without surrounding weeds. Leaf area, leaf biomass, and root biomass was similar whether weeds were removed at the two true-leaf stage (approximately 330 GDD after planting) or allowed to remain until sugar beet harvest (approximately 1,240 GDD after planting). Adding weeds at the two true-leaf stage and leaving them until harvest (~1,240 GDD) reduced sugar beet leaf and root biomass by 18% and 23%, respectively. This work suggests sugar beet responds early and near-irreversibly to weed presence and has implications for crop management genetic improvement.

Biosurfactant from endophytic Bacillus pumilus 2A: physicochemical characterization, production and optimization and potential for plant growth promotion.

BACKGROUND: Microbial surfactants called biosurfactants, thanks to their high biodegradability, low toxicity and stability can be used not only in bioremediation and oil processing, but also in the food and cosmetic industries, and even in medicine. However, the high production costs of microbial surfactants and low efficiency limit their large-scale production. This requires optimization of management conditions, including the possibility of using waste as a carbon source, such as food processing by-products. This papers describes the production and characterization of the biosurfactant obtained from the endophytic bacterial strain Bacillus pumilus 2A grown on various by-products of food processing and its potential applications in supporting plant growth. Four different carbon and nitrogen sources, pH, inoculum concentration and temperature were optimized within Taguchi method. RESULTS: Optimization of bioprocess within Taguchi method and experimental analysis revealed that the optimal conditions for biosurfactant production were brewer's spent grain (5% w/v), ammonium nitrate (1% w/v), pH of 6, 5% of inoculum, and temperature at 30 °C, leading to 6.8 g/L of biosurfactant. Based on gas chromatography-mass spectrometry and Fourier transform infrared spectroscopy analysis produced biosurfactant was determined as glycolipid. Obtained biosurfactant has shown high and long term thermostability, surface tension of 47.7 mN/m, oil displacement of 8 cm and the emulsion index of 69.11%. The examined glycolipid, used in a concentration of 0.2% significantly enhanced growth of Phaseolus vulgaris L. (bean), Raphanus L. (radish), Beta vulgaris L. (beetroot). CONCLUSIONS: The endophytic Bacillus pumilus 2A produce glycolipid biosurfactant with high and long tem thermostability, what makes it useful for many purposes including food processing. The use of brewer's spent grain as the sole carbon source makes the production of biosurfactants profitable, and from an environmental point of view, it is an environmentally friendly way to remove food processing by products. Glycolipid produced by endophytic Bacillus pumilus 2A significantly improve growth of Phaseolus vulgaris L. (bean), Raphanus L. (radish), Beta vulgaris L. (beetroot). Obtained results provide new insight to the possible use of glycolipids as plant growth promoting agents.

A Comparison of the Effect of Lead (Pb) on the Slow Vacuolar (SV) and Fast Vacuolar (FV) Channels in Red Beet (Beta vulgaris L.) Taproot Vacuoles.

Little is known about the effect of lead on the activity of the vacuolar K+ channels. Here, the patch-clamp technique was used to compare the impact of lead (PbCl2) on the slow-activating (SV) and fast-activating (FV) vacuolar channels. It was revealed that, under symmetrical 100-mM K+, the macroscopic currents of the SV channels exhibited a typical slow activation and a strong outward rectification of the steady-state currents, while the macroscopic currents of the FV channels displayed instantaneous currents, which, at the positive potentials, were about three-fold greater compared to the one at the negative potentials. When PbCl2 was added to the bath solution at a final concentration of 100 µM, it decreased the macroscopic outward currents of both channels but did not change the inward currents. The single-channel recordings demonstrated that cytosolic lead causes this macroscopic effect by a decrease of the single-channel conductance and decreases the channel open probability. We propose that cytosolic lead reduces the current flowing through the SV and FV channels, which causes a decrease of the K+ fluxes from the cytosol to the vacuole. This finding may, at least in part, explain the mechanism by which cytosolic Pb2+ reduces the growth of plant cells.

Genetic diversity among cultivated beets (Beta vulgaris) assessed via population-based whole genome sequences.

BACKGROUND: Diversification on the basis of utilization is a hallmark of Beta vulgaris (beet), as well as other crop species. Often, crop improvement and management activities are segregated by crop type, thus preserving unique genome diversity and organization. Full interfertility is typically retained in crosses between these groups and more traits may be accessible if the genetic basis of crop type lineage were known, along with available genetic markers to effect efficient transfer (e.g., via backcrossing). Beta vulgaris L. (2n =18) is a species complex composed of diverged lineages (e.g., crop types), including the familiar table, leaf (chard), fodder, and sugar beet crop types. Using population genetic and statistical methods with whole genome sequence data from pooled samples of 23 beet cultivars and breeding lines, relationships were determined between accessions based on identity-by-state metrics and shared genetic variation among lineages. RESULTS: Distribution of genetic variation within and between crop types showed extensive shared (e.g. non-unique) genetic variation. Lineage specific variation (e.g. apomorphy) within crop types supported a shared demographic history within each crop type, while principal components analysis revealed strong crop type differentiation. Relative contributions of specific chromosomes to genome wide differentiation were ascertained, with each chromosome revealing a different pattern of differentiation with respect to crop type. Inferred population size history for each crop type helped integrate selection history for each lineage, and highlighted potential genetic bottlenecks in the development of cultivated beet lineages. CONCLUSIONS: A complex evolutionary history of cultigroups in Beta vulgaris was demonstrated, involving lineage divergence as a result of selection and reproductive isolation. Clear delineation of crop types was obfuscated by historical gene flow and common ancestry (e.g. admixture and introgression, and sorting of ancestral polymorphism) which served to share genome variation between crop types and, likely, important phenotypic characters. Table beet was well differentiated as a crop type, and shared more genetic variation within than among crop types. The sugar beet group was not quite as well differentiated as the table beet group. Fodder and chard groups were intermediate between table and sugar groups, perhaps the result of less intensive selection for end use.

Impact of sugar beet seed priming using the SMP method on the properties of the pericarp.

BACKGROUND: This study determined the effects of two solid matrix priming methods on changes in the characteristics of two lots of the same variety of sugar beet fruits that differ in the level of vigour. RESULTS: Seed treatment within each level of vigour did not significantly affect helium and apparent density, total pore volume and total porosity. However, there was a tendency to increase porosity due to priming. This is probably why seed priming significantly increased mesopore diameter in both high and low vigour seeds. These changes increased the water content in the pericarp and the seeds and increased the water potential during germination. The high level of electrical conductivity of the fruit extracts was associated with low seed vigour. Low vigour resulted in higher humidity of the pericarp and decreased seed moisture and was also associated with lower water potential of the pericarp and seeds. CONCLUSIONS: A significant difference in the water content in the pericarp and seeds was indicative of imbibition and problems with water flow between these centres, which resulted in a low water diffusion coefficient of the pericarp. This low water diffusion coefficient was correlated with the prolongation of the seed germination time.

The RsRlpA Effector Is a Protease Inhibitor Promoting Rhizoctonia solani Virulence through Suppression of the Hypersensitive Response.

Rhizoctonia solani (Rs) is a soil-borne pathogen with a broad host range. This pathogen incites a wide range of disease symptoms. Knowledge regarding its infection process is fragmented, a typical feature for basidiomycetes. In this study, we aimed at identifying potential fungal effectors and their function. From a group of 11 predicted single gene effectors, a rare lipoprotein A (RsRlpA), from a strain attacking sugar beet was analyzed. The RsRlpA gene was highly induced upon early-stage infection of sugar beet seedlings, and heterologous expression in Cercospora beticola demonstrated involvement in virulence. It was also able to suppress the hypersensitive response (HR) induced by the Avr4/Cf4 complex in transgenic Nicotiana benthamiana plants and functioned as an active protease inhibitor able to suppress Reactive Oxygen Species (ROS) burst. This effector contains a double-psi beta-barrel (DPBB) fold domain, and a conserved serine at position 120 in the DPBB fold domain was found to be crucial for HR suppression. Overall, R. solani seems to be capable of inducing an initial biotrophic stage upon infection, suppressing basal immune responses, followed by a switch to necrotrophic growth. However, regulatory mechanisms between the different lifestyles are still unknown.

The biochemistry underpinning industrial seed technology and mechanical processing of sugar beet.

MAIN CONCLUSION: Seed-processing technologies such as polishing and washing enhance crop seed quality by limited removal of the outer layers and by leaching. Combined, this removes chemical compounds that inhibit germination. Industrial processing to deliver high-quality commercial seed includes removing chemical inhibitors of germination, and is essential to produce fresh sprouts, achieve vigorous crop establishment, and high yield potential in the field. Sugar beet (Beta vulgaris subsp. vulgaris var. altissima Doell.), the main sugar source of the temperate agricultural zone, routinely undergoes several processing steps during seed production to improve germination performance and seedling growth. Germination assays and seedling phenotyping was carried out on unprocessed, and processed (polished and washed) sugar beet fruits. Pericarp-derived solutes, known to inhibit germination, were tested in germination assays and their osmolality and conductivity assessed (ions). Abscisic acid (ABA) and ABA metabolites were quantified in both the true seed and pericarp tissue using UPLC-ESI(+)-MS/MS. Physical changes in the pericarp structures were assessed using scanning electron microscopy (SEM). We found that polishing and washing of the sugar beet fruits both had a positive effect on germination performance and seedling phenotype, and when combined, this positive effect was stronger. The mechanical action of polishing removed the outer pericarp (fruit coat) tissue (parenchyma), leaving the inner tissue (sclerenchyma) unaltered, as revealed by SEM. Polishing as well as washing removed germination inhibitors from the pericarp, specifically, ABA, ABA metabolites, and ions. Understanding the biochemistry underpinning the effectiveness of these processing treatments is key to driving further innovations in commercial seed quality.

Hydro-thermal priming enhance seed germination capacity and seedling growth in sugar beet.

Seed priming improves seed performance in many crop species. In this study, the influence of hydrothermal priming on seed parameters of sugar beet is investigated in both laboratory and field conditions. In the laboratory, the treatments consist of a combination of cultivars (Arya and Shokoofa), hydro-priming at two temperatures (10 and 15 °C) for 6, 10, 14, 18, 22 hours. Germination traits and seedling growth were measured for determination of optimum hydro-thermal priming. Also, the protein pattern in the optimum hydro-thermal priming treatments and unprimed seeds were compared by electrophoresis. In the field experiment, the percentage and rate of emergence of primed and unprimed seeds were measured. Results showed that hydro-thermal priming had a positive effect on final germination percentage, mean germination time and uniformity of germination. Optimum hydro-thermal priming time and the temperature were 6 and 10 hours at 15 °C for Shokoofa and Arya cultivars respectively. Hydro-thermal priming increased the seed emergence percentage in the field by 15%. There was no significant difference in protein pattern between primed and unprimed seeds. In general, hydro-thermal priming not only increases sugar beet seed germination in the laboratory but also has a more positive effect on the emergence in the field condition.

CMS-G from Beta vulgaris ssp. maritima is maintained in natural populations despite containing an atypical cytochrome c oxidase.

While mitochondrial mutants of the respiratory machinery are rare and often lethal, cytoplasmic male sterility (CMS), a mitochondrially inherited trait that results in pollen abortion, is frequently encountered in wild populations. It generates a breeding system called gynodioecy. In Beta vulgaris ssp. maritima, a gynodioecious species, we found CMS-G to be widespread across the distribution range of the species. Despite the sequencing of the mitochondrial genome of CMS-G, the mitochondrial sterilizing factor causing CMS-G is still unknown. By characterizing biochemically CMS-G, we found that the expression of several mitochondrial proteins is altered in CMS-G plants. In particular, Cox1, a core subunit of the cytochrome c oxidase (complex IV), is larger but can still assemble into complex IV. However, the CMS-G-specific complex IV was only detected as a stabilized dimer. We did not observe any alteration of the affinity of complex IV for cytochrome c; however, in CMS-G, complex IV capacity is reduced. Our results show that CMS-G is maintained in many natural populations despite being associated with an atypical complex IV. We suggest that the modified complex IV could incur the associated cost predicted by theoretical models to maintain gynodioecy in wild populations.

Microevolution or wide tolerance? Level of stress proteins in the beet armyworm Spodoptera eqigua hübner (Lepidoptera: Noctuidae) exposed to cadmium for over 150 generations.

The aim of this study was to investigate whether the cadmium tolerance developed in the beet armyworm Spodoptera exigua selected for over 150 generations may be related to synthesis of the stress proteins metallothioneins (Mts) and 70 kDa heat shock proteins (HSP70). To achieve this, six S. exigua strains (control, k), 150-generation Cd exposure strain (cd), and four 18-generation Cd exposure strains differing in Cd concentration (cd44, cd22, cd11, cd5) were reared. Stress protein level was measured in the midgut of the 5th larval stage after 1-6, 12 and 18 generations. Cd contents was measured in the pupae. Unlike Cd concentration, which depended on metal contents in food but was not generation-dependent, the pattern of Mts and HSP70 concentrations changed in experimental strains from generation to generation. Stress protein levels in the insects exposed to the highest Cd concentration (the same as in the 150-generation Cd exposure strain), initially higher than in the control strain, after the 12th generation did not differ from the level measured in the control strains. It seems therefore that stress proteins play a protective role in insects of lower tolerance to cadmium. The tolerance developed during multigenerational exposure probably relies on mechanisms other than Mt and HSP70 synthesis.

Risk assessment of frost damage to sugar beet simulated under cold and semi-arid environments.

In the semi-arid climatic conditions, water shortage is a key factor to generate crop production. Planting in autumn and winter and using precipitation can help cope with the problem. But in the semi-arid areas with cold winter, frost is another limited factor affecting crop production. For this purpose, in the present study, a simple and universal crop growth simulator (SUCROS) model was used to estimate the potential yield of sugar beets and frost damage from 1993 to 2009 for four autumn sowing dates (2 October, 17 October, 1 November, and 16 November) and two spring dates (6 March and 6 May) in eight locations (Birjand, Bojnord, Ghaen, Mashhad, Torbat-e Heydarieh, Neyshabor, Torbat-e Jam, and Ghochan) of the Khorasan province in northeastern Iran as a semi-arid and cold area. There was a large variability between locations and years in terms of frost damage. The crop failure from frost for the autumn sowing dates ranged from 62.5 to 100% at Neyshabor and Ghochan, respectively. Although autumn sowing dates performed better than spring sowing dates in terms of fresh storage organ yield (~ 109.9 t ha-1 vs. ~ 78.4 t ha-1), the risk of frost stress under autumn sowing dates was high at all studied locations. To maximize potential yield and minimize frost risk, sugar beet farmers under semi-arid and frost-prone conditions in the world such as Khorasan province should choose optimum sowing dates outside the high frost risk period to avoid crop damage. The last frost day under these areas normally happened between the 15th and 28th of February, after which no frost events occurred. Accordingly, it is recommended to farmers to sow sugar beet after the period during which no frost risk for sugar beet occurred.